The present invention relates to a method of and a device for detecting an angular position of a rotatable machine part, for example a rotary position of a crankshaft of an internal combustion engine. From the detection of the corresponding actual angular position of the crankshaft, signals are produced which can be used for generation of an ejection or an ignition pulse.
Methods of and devices of the above mentioned general type are known in the art. The position of the crank shaft is determined by counting of the incremental teeth on a transducer wheel of a crankshaft. A rotary angle transducer is necessary for accurate association of the crankshaft position. This can be an inductive pulse transducer which supplies an output signal to a control device when a reference mark, for example designed as a pin, a hole or a recess, passes by the sensor. One output signal can be produced per one revolution of the crankshaft.
The teeth of a special tooth wheel on the crankshaft can be scanned by an inductive pulse transducer. Thereby a change of the magnetic flux can be obtained, which induces an alternating voltage. This alternating voltage can be evaluated by means of a control device.
When the individual teeth are arranged on the tooth wheel at equidistant spaces from one another, two teeth on the toothed wheel are removed for defining a reference position, for example 0xc2x0. Conventional transducer wheels are usually identified as 60-2 or 120-2 increment wheels. With the 60-2 transducer wheel all 360 xc2x0:60, and thereby 6xc2x0 angular region forms an increment pulse. A simplified resolution of the angular distance can be obtained by a controller on the control device, whereby at any angles events such as ignition or injection steps can be performed.
With an electro hydraulic control of gas exchange valves, individual adjustment units are provided on the gas exchange valves, and their control is performed coupled non mechanically to the crank or cam shaft, but instead their control is performed exclusively via a control device. With the switching pulses produced by the control device which are angle-dependent from the crankshaft position, the electrohydraulic adjustor or the electromagnetic adjuster is controlled. It must be guaranteed that the switching pulses are produced at the correct angles. Otherwise in the internal combustion engine collisions can occur between an extended gas exchange valve and a piston which is movable in the upper dead point in the cylinder. In the same way, collisions between two open, oppositely arranged gas exchange valves are possible.
Accordingly, it is an object of present invention to provide a method of and a device for detection of an angular position of a rotatable machine part, which avoids the disadvantages of the prior art.
More particularly, it is an object of present invention to provide a method of and a device for detection of a rotary position of a transducer wheel in which faulty angular informations resulting from disturbances or failures can be avoided.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in the method in which the position of the transducer wheel is simultaneously detected by an increment transducer and by means of an absolute angle transducer.
The use of two angle information transducers which operate in accordance with different physical principles provides a significance increase of the disturbance prevention of the angle information detection. During a disturbance only one angle transducer or the signal transmission from a transducer can be further processed with the corresponding different information. The individual informations, or in other words the information of only the increment transducer or the information of only the absolute angle transducer, can be plausibilized by performing of a continuity testing.
The difference signal generation and signal transmission increases the reliability and the availability of the angle information detection decisively. Thereby, in extreme critical angle regions adjustment events, such as for example the opening of a gas exchange valve and its closing operate in a reliable manner. The control of the adjusters with gas exchange valves can be reliably performed in this manner within the electrohydraulic valve control or the electromagnetic valve control.
The use of increment transducer as a primary transducer provides on the one hand the detection of a high-actual angle information of the part to be detected, and on the other hand after a certain disturbance requires a new synchronization of the increment transducer. The use of an additional absolute angle transducerdetects after certain disturbance directly again the rotary movement of a transducer wheel, so that a correct angle information is transmitted to the control device without requirements for a new synchronization.
The use of an absolute angle transducer provides in the position of the motor stoppage an inquiry via the angle position of the crankshaft. Thereby during the starting phase, for example all gas shuttle valves on an internal combustion must remain closed, until the increment transducer is synchronized. Thereby a substantially shorter starting phase is obtained with a combustion engine, in which due to the injection which is corrected with respect to the angle position and a cylinder, a faster start is possible. Moreover, the exhaust gas emission is considerably reduced by shortening of the starting phase. Together with a direct injection, a direct start of an internal combustion engine is possible (without a starter).
Furthermore, with the method in accordance with the present invention and the inventive device, a fast recognition of a low rotary speed of the internal combustion engine is provided, so that the electric fuel pumps, ignition and injection pulses are switched off early by the control device. Finally, with the proposed inventive solution, the advantages are provided in an early and reliable recognition of the rotary direction, so that during stalling of the combustion engine the valve control as well as outputting of the ignition and injection signals do not occur.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.